Fogging devices, used to generate an insecticide fog, for example, and utilizing the pulse-jet (resonant intermittant combustion) principle, are well known in the prior art. An example of such structure is disclosed in Tenney et al U.S. Pat. No. 2,857,332 and the pulse jet engine operation is there explained in some detail. A fogging apparatus utilizing a resonant, intermittant combustion device, a fuel supply, an insecticide supply and a starting device is disclosed in Curtis U.S. Pat. No. 3,151,454. The apparatus of the present invention represents an improved version of such prior art devices.
The apparatus of the present invention provides a thermal barrier between the engine and the fuel and insecticide tank components. The engine has a housing configuration and air vent orientation such that convection air currents reduce or eliminate the substantial temperature rise of parts of the apparatus occuring after engine shut-down, a difficulty which has plagued prior art devices. The fuel valve component provides improved fuel air atomization and mixing and substantially eliminates back-flow or blow-back of raw fuel through the air intake, a condition heretofore inherent in pulse jet engine operation. The valve which controls flow-inducing pressurizing of the insecticide tank is provided with a vent which functions to bleed off pressure in the insecticide tank after engine shut-down, an added safety feature. The control valve, metering the flow of insecticide at a selected rate, utilizes an integrally formed conically shaped valve member of a suitable elastomeric material with a circular bead above the conical portion so that sealing of both the stem and the valve seat is accomplished by the single valve member. Several constructional features, including a vapor trap in the fuel feeding line, prevent fuel and fuel vapor from migrating into proximity with hot engine parts immediately after engine shut-down. Post-shut down ignition of fuel, a difficulty in prior art structures, is thus prevented. The apparatus is provided with additional constructional improvements referred to in the subsequent, detailed description of the device.